1. Field of the Invention
The present invention relates generally to the measurement of peak values of analog signals and, more particularly, to a method and apparatus for detecting the peak value of an analog signal which has been converted into digital form. The invention is particularly well suited for but not limited to use with analog-to-digital converters of the dual-slope integrating type.
2. Description of the Prior Art
A variety of analog and digital techniques exist for detecting peak values of analog signals. In a common analog technique the rate of change of the analog signal is developed and a peak is indicated when the rate of change passes through zero. However, this analog arrangement is unreliable at low input signal levels since the rate signal developed from a low analog signal may be insufficient to operate the zero pass-through detector. In addition, the zero detector is subject to the well known d.c. offset problems of amplifier circuits. Moreover, it is possible for noise or random variations of the input to be detected as peaks.
Common digital techniques typically employ an analog-to-digital converter, such as a dual-slope integrating converter, for converting the analog signal into digital form in combination with circuitry for analyzing the digital information to determine if a peak has been attained. Such converters typically include a digital pulse source together with counting and timing means for generating the digital pulse counts, a buffer register of some kind for temporarily storing pulse count values, and a display for displaying the pulse count values stored in the buffer register. While the digital arrangements will satisfactorily detect peak values, they are unduly complicated and require extensive additional circuitry beyond that required to execute the analog-to-digital conversion itself.